Batboard

OK, I know there's some smart battery people out here.

I've ordered a OEM dual battery setup from GM. 95% of it is sitting in front of me. Two 34/78 Series Optima Red Tops are ready and waiting too.

This is for a 2003 V8 6.0L and is supposed to be a drop in upgrade for the truck. Dual battery installed at the factory wasn't an available option on a gas powered suburban in 03.

If I do have everything ( had to order each piece seperate) the batteries are tied together at the starter through a fuse and high capacity relay. Relay is missing the weather pak harness for it, which I'll assume is for ignition sense. Another small 12ga wire goes from the other side of the fuse over to the main underhood/relay fuse panel. What is that supposed to do?

I assume this is an always on tied together both batteries start the engine setup when the relay is powered. Right?

Seriously wondering if I should have ordered the WranglerNW power products dual setup instead. Their systems allows for control over what batteries are connected to what, either both charged single start, both off but charged or dual on for starting or heavy draw like operating a winch.

Not sure if this will be any help or not, but here it goes.

I had a 1994 GMC 3/4t pickup that I ordered with the factory dual battery setup.

The second battery was connected through the relay to the original battery. The relay closed when the ignition was on to facilitate charging of the second battery. I don't recall exactly where the tie in was.

There was a 12ga or so wire that left the second battery and tied into the trailer wiring harness somewhere. The second battery was set up from the factory to feed power via the trailer harness to the trailer. I presume to supply power to a camper.

I only used mine to power a winch, and radios. When the ignition was off, I didn't have to worry about discharging the starting battery. I was always going to wire in a switch to manually operate the relay, and upgrade the cables so I could start off the second battery, but I ended up selling the truck before I did that. I just carried a set of jumper cables, and could just jumper between batteries to get started.

Hope that helps.

This setup is different.

It does appear that both batteries are used for starting, but some odd reason they've tied at the Starter and they're charginging the battery off the underhood fuse/relay box instead of directly from the point where the alternator is attached. Makes for an odd loop that I don't think is good to have. Couple that with the wimpy 6ga wires and I really do not understand why its done this way.

I just got off the phone with Wrangler NWpower products and their setup is what I had originally expected, batteries tied directly together (like a diesel for heavy loads) and which can be controlled and or isolated as needed.

Looks like all I'm keeping from GM is the battery tray, hold down and bolt. Their dinky wires are going back.

The dual battery setups for Diesel and gas are different. The Diesel units are tied together all the time because they are a "dual" setup, while the gas versions use the relay to connect the "auxiliary" battery to the charging system. The dual setup uses a fuse in the line between 'em to keep the possibility of a really dead (cell shorted, etc) battery from taking the juice from the good one to ground and making the numbers 9-1-1 significant.

Two versions of the gas unit exist depending on the application and the year model. On one, the relay is actuated by the ignition switch in either the Accessory position or the ON position. The other is actuated only when the switch is in the ON position. You can tell the "aux" version from the "dual" set up with just a glance because, unlike the "dual" setup, the "aux" battery will be a different size from the main battery, and usually smaller than the main. **NOTE! The relay supplied is only capable of carrying charging current to the aux battery, so a protective device is also in the line to keep that 9-1-1 thing to a minimum.

Dual setups must use batteries of equal capacity or one will suck the life out of the other, and even then they still do it. No two batteries are exactly equal, so some method of separating them has to be in place or they'll continually headbutt each other. It's just like water flowing back and forth between two levels that keep changing. Whichever battery is "lower" will pull current from the other, and since no two batteries are exactly equal, they never reach equilibrium. This is true inside the battery from cell to cell, too. This is also why two mongo batteries on a Diesel won't last as long tied together as either would last by itself or separated when not needed.

For radio stuff, the aux battery type of setup is preferable to dual anyday. I've had the aux version with a switch in the line to switch the relay's voltage source from the Acc/ON line to a bypass switch so I can choose my voltage source as choice or auto, but I'm also using one of Standard Electrical's elephantine continuous duty solenoid switches to do the honors. Part #SS584, available at Advance Auto or other parts houses, under 35 bucks. You can use any of their continuous duty solenoids, and the numbers may have changed, but SS584 is the number that sticks in my mind. Some are self-grounding through the body and some have a separate ground terminal. DO NOT confuse this switch with an intermittent duty Ford-style starter switch that looks very similar or you will need to keep that 9-1-1 thingie nearby.

Whichever version of the continuous duty models you find should work just fine, but I prefer the all steel body units over the plastic body versions. Make sure you mount 'em vertically or they'll collect moisture in the coil body and that 9-1-1 thingy comes into play again when passing large amounts of current.

So, a solenoid, some cables, a battery, a control switch, a fuse and holder and small control wire should get you an aux setup with little complexity or expense. The Optimas are the shiznit, been using them for years in my 4x4s.

As for the Wranger stuff, it's great. Fully optioned, that gives you dual-isolated-auxiliary choices all in one by choosing the switch position. Kewl.

Bruce,

That's exactly what I thought over the GM setup. I'm working backwards from parts diagrams so we (service manager) are kinda in the dark.

The dealer thinks both batteries will be used when in the ON position and its isolated only when the truck is off. Isnt' that self defeating then? No control switch either. This should be the DUAL setup because of the large relay, yet the wire coming in to charge only goes directly to a fuse.

Whole thing doens't make sense so is this some sort of goofy hybrid design?

I'll get dealer pricing on the WranglerNW power products setup, which as you describe allows single starting with dual charge, single start, single charge and dual start dual charge modes that are user selectable.

I'll make my own cables out of large ga wire and still end up cheaper than GM.

Hopefully my service manager won't hate me too much for returning this stuff.

apco25 wrote:The dealer thinks both batteries will be used when in the ON position and its isolated only when the truck is off.

Yes. Our '98 burb with a gas 350 here at work has a dual battery setup. Passenger side battery is starting/OEM systems, Driver side battery is accessory use only. Only the Passenger battery is for starting, the other is an accessory battery that is disconnected via solenoid when the ignition is off. All the emergency equipment and radio is attached to the accessory battery. If the truck isn't running, the accessory battery is completely stand-alone. There is a red 8 or 6 gauge cable coming from the main battery over to the solenoid, thru a dual fusible link, to the accessory battery.

I can't believe much has changed with your 2003 other than wiring locations.

What I see as a problem with the GM setup is that it's controlled and fused through the vehicle harness, which doesn't give you any options. A battery acts as a large capacitor, and when you take everything on the comm side directly to the battery, the capacitive effects of the battery help keep the noise out of your added circuitry. My years of experience tells me that using the vehicle's accessory harness and fuse panel for any of the aux battery wiring is just asking for trouble.

Once upon a time there was a GMC pickup ('88 vintage) that was used by the comm supervisor for a large utility company. This truck had the factory aux battery and the requisite ton of comm gear on it, and it also had alternator whine on one radio that was impossible to remove. The radio had an amplified speaker that always seemed to be susceptible to noise no matter what vehicle it was mounted in, and their techs had made several attempts to lose the noise. They had done an excellent job of grounding everything and pieces parts to other pieces parts to a common location, but all was in vain.

When they finally brought it to me, I went out and bought the SS584(?) solenoid and proceeded to buiild an isolator system for the truck's aux battery. Got it installed, took it out for a spin, and no more noise. I probably could have just removed the factory relay control wiring and installed my own, but that relay and tiny wiring just bothered me no end, so I started over.

The comm supervisor was so paranoid about ending up with the noise on the radio in a new truck that he passed up the opportunity on a new truck twice before they made him turn it in. He brought it to us to remove the system we had installed, and to hook the factory wiring back up. I later installed the setup on his new truck.

I added a battery to my truck.
To tie it into the system, I put a solenoid (rated for continuous duty, and cranking amps) with a 3 position switch on the dash, on, off and on with ignition.
All the radios are run from the aux battery with their own fuse panel.
It is almost always left in the on with ignition position, unless I need to crank with it, then I switch off the main switch to all the radios.
Simple.

Thanks to the the tech as WranglerNW power products and email from Jim I've decided to send back the GM kit.

The tiny gauge wire and the odd way its hooked up just doesn sit well with me.

I just don't understand how the original battery has 2ga wire, yet the AUX battery is tied to the starter but only via 6ga?

Either that's just cheap or the GM designers are playing the wire gauge size game to the max.

What I wanted all along was either a true dual setup like a diesel or a dual setup that can be switch isolated as needed.

Upon further investigation the 12ga lead goes to the trailer aux power stud on the main underhood fuse/relay box. The more I look at it does it appear this was meant more for trailer use than anything else. Yet it is tied to the starter!

I'll just be moving my front and rear 4ga leads to the 2nd battery and call it a day.

Half the confusion wouldn't have resulted if I could have gotten a hold of better info (schematics) instead of working backwards from a parts exploded view.

I'd have to agree, that was my plan, before I sold the truck. The GM set up seems to be just for trailers. The Wrangler products are nice, but with the right tools, you can build your own. From what I have seen of your installations, you can do a much better job, cheaper, and get exactly what you want.

I'd bet it going to be a nice set up when it is done.

I'm sure you know this, but one of the first things I did on my 94GMC was to upgrade the cheesy body ground jumpers coming off the batteries.

Before you do hear me out. I recently purchased an xantrex pathmaker (or pathfinder dont remember) for dual battery isolation. This consists of a 200 amp continous duty solenoid and a control box. This box uses voltage to connect the batterys, to insure that the starting battery recieves full charge before the radio battery starts charging.

This is the way i wired it:

All 4GA cable

Batt1: Optima red top
My chevy uses side posts so i got a 3/8 stud to top post cable and ran that into one side of the solenoid.
Batt2: Optima yellow top
Used side post terms there to connect to other 3/8 stud of solenoid.
Top post goes into cab for radios and lights.
Altenator: (this is not required for proper operation)
I ran a cable from the output stud to the solenoid on the red battery side so that it charges that DIRECTLY, as well as the yellow once the solenoid closes.

There are 3 wires that run to the control box, B1, B2, Coil.
B1 and B2 are just voltage readings for bolth batterys.
Coil is for closing the solenoid.

You have pots that are used to control the engage disengage and hi voltage shutoff voltages. There is also a switch to turn it off, auto, on.

If you need a diagram or need pics i would be happy to explain it to you. Email me at [email protected]

Yep, very similar if not identical to what WranglerNW Power Products is sending me.

I'll email you anyway for comparison.

Hey guys, why all this mucking around with the solenoids? Why don't you try looking at how the fire trucks and ambulances are done these days.

All the heavy duty public safety and medic systems are done with diode battery isolators. The 2 batteries are always being charged while the engine is running, but the loads are not tied together. This way you leave the normal vehical battery alone and put all your external load on the second battery. You don't have to worry about killing the start battery.

Only point to keep in mind is that you need a heavy duty alternator to be able to handle the load of charging the extra battery load. This would normally be a 120 to 175 amp alternator requirement.

You can also install an alternator with the ability to have a dual output. This would negate having to install a dual battery isolator. Just install the heavy wiring needed from the alterenator to the battery.

I have run this dual battery alternator setup in a couple of trucks and com vans and they work slick. Pull out the original alternator, slip in the new one and use the original wiring that was there for the normal electrical system. Then just add the wires needed for the second battery and it's load.

You can even install a solenoid with a push button to be able to tie both batteries together for an emergency start for those that have managed to kill the normal battery.

Jim

apco25 wrote:Yep, very similar if not identical to what WranglerNW Power Products is sending me.

I'll email you anyway for comparison.

Yeah well Diode isolated systems do have a voltage drop across them. Its mentioned here and in other posts on the subject.


I was looking fora true dual system for starting and heavy amp loads like winching etc, not just a place to run all the radios and other stuff to.

I have the WranglerNW setup in my Tahoe and it works great. I run all of my radios, lighting, stereo, and computer on the secondary battery. Their wiring harness is nice because its simple to install and the solenoid with the switch works great. Its nice to be able to bridge both batteries when I am running the M15000 winch.

Yep, that's exactly how I want to use mine and will.

Thanks for all the good comments. I'll post pics once all the parts arrive.

If you want any pics in the meanwhile let me know and I can take a few. My install was a bit of a project because of the emissions equiptment where the battery needed to go. Once that was relocated it was easy.

Sure post away, always good to see other setups. No problems in the burb as there is an nice factory empty spot for the 2nd battery tray.

Notice the momentary switch near the ignition switch. It is the emergency boost switch, connecting the auxillary battery to the main battery while cranking to help start the vehicle.

Alt battery location at sufficent remote locations which will require 150 breakers to protect against shorts to the cable between the two in case of a collision, etc.

Diode size should be 3 amps, 500v rated. Two diodes needed, one at the switch AND one at the solenoid. Band side of the solenoid diode to face POSITIVE and the other end to the ground terminal on the solenoid. Solenoid diode prevents back-spiking in the electrical system from the solenoid at the moment of deactivation.

Hope it helps,
Sean